A gun with smooth-bore barrle, whatever its operating system, necessarily has feed (recocking) assemblies such as to cause, at every fired round, the passage of a new cartridge from the magazine, generally tubular in shape, into the cartridge chamber of the barrel.
If this passage occurs automatically at each fired round, the gun will be termed semiautomatic in operation; if the passage occurs, at each fired round, manually, by means of the movement of the cocking rod, the gun will be termed manually or pump operated.
In order to achieve, in either case, the passage of the cartridge from the magazine to the cartridge chamber of the barrel, the backward opening stroke of the bolt assembly has always been used, in various manners, to synchronize the movements of the lever (or levers) for stopping the cartridge in the magazine, for the exit of a single cartridge at a ttime, with those of a lifter cup on which said cartridge is arranged, in exiting from the magazine, to be raised to a position suitable for introduction into the barrel.
Various feed systems are known, suitable for the type of operation (semiautotmatic or pump) with which the firearm is provided, generally comprising two levers for stopping the cartridge in the magazine and shaped so as to be moved by the bolt of the firearm, or even partly arranged directly on said bolt.
In all these cases, suitable buttons, mounted separately, prepare the firearm, in a more or less complicated manner, for the manual passage of the cartridge in the barrel from the magazine or for the momentary locking of the cartridges in the magazines for changing the one in the barrel.
These systems are extremely complex and expensive and are generally used only on firearms with pump operation.
Simpler feed systems are also known, havingn a single cartridge stop lever, developed with the onset of the semiautomatic operating system of the firearm, but, mostly, are only operable with this operating system and do not allow the manual passage of the cartridges from the magazine to the cartridge chamber of the barrel of said firearm, unless highly complicated and delicate mechanims are used.